The present invention relates to a cold-start apparatus for alcohol-fueled internal combustion engines having externally supplied ignition. The apparatus has an alcohol fuel cycle embodied by a delivery route beginning at an alcohol fuel tank and leading to the engine distributor tube from whence it leads back to the alcohol fuel tank. A feed device, such as an alcohol fuel pump, is provided in this cycle, and injection valves for injecting alcohol fuel communicate with the distributor tube and with the respective combustion chamber of the engine, and the combustion chambers are supplied with combustion air via an intake tube. The apparatus also has a gasoline cycle including a gasoline tank; a gasoline delivery line beginning at the gasoline cycle is provided to deliver gasoline to or near the combustion chambers, to reinforce the combustion process initially, until combustion can be maintained by the alcohol fuel alone.
The invention also relates to a cold-start method that can be used with this cold-start apparatus.
As is already well known in the art, engines operated with alternative fuels such as alcohol are not capable of starting at low temperatures, in particular at temperatures lower than 10.degree. C. This is because initially, combustion is insufficient for starting the engine, because of the low temperature of the alcohol fuel and of the combustion chambers. The operative physical principle is that the alcohol has high latent heat of evaporation an therefore, as long as it is cold, is incapable of evaporating sufficiently to maintain the aforementioned initial combustion. Even if the combustion at least begins at low temperatures, the problem still exists of maintaining it, because a delayed explosion of the mixture of alcohol fuel and air inside the chamber occurs, leading to frequent failures in engine operation; the engine repeatedly stops operating and the injected quantity of alcohol fuel is increased. If attempts to start the engine are pursued, not only will the engine become flooded, but there is a severe strain on both the electrical and the mechanical parts.
To overcome these problems, which arise in alcohol-fueled internal combustion engines, systems that operate on two principles, below, have been developed.
The first principle is to heat the alcohol fuel, prior to its entry into the combustion chamber, to a temperature at which the alcohol fuel can evaporate and hence can maintain the combustion.
The second principle is to inject a predetermined quantity of gasoline directly into the combustion chambers of the engine. In that case, the combustion is initially reinforced, because the latent heat of vaporization of the gasoline is much lower than that of the alcohol fuel, so that a smaller amount of the evaporated gasoline can suffice for starting the engine, and the engine temperature becomes sufficient for combustion to begin, which in turn enables the engine to warm up to a temperature at which the combustion can be maintained with alcohol alone.
Although the known systems that operate on these principles have represented a functional solution to the problem thus far, they still have many disadvantages. Because of the delayed explosion of the alcohol fuel and air mixture in this transition phase between starting and normal engine operation, frequent engine failure occurs, which is expressed as rpm fluctuations, vibration, bucking, and subsequent and repeated "dying" of the engine; this may necessitate using the starting aid, and may even necessitate repeated attempts at starting.
Conventional systems of this kind have still other disadvantages that must be overcome. Engines that operate by the first principle above require the use of heaters for the fuel delivery lines leading to the combustion chambers. Not only are they impractical, but installing them entails additional difficulty and expense. Moreover, the supply of current to the heaters must be done from the battery of the system before the starter is actuated, s that the battery is discharged; therefore, problems can arise because there is insufficient energy left for actuating the starter and subsequently maintaining reliable ignition.
The conventional cold-start systems that operate on the second of the above principles have major disadvantages as well. Besides those already mentioned, there is the disadvantage that auxiliary mechanical parts, like the starter, and the electrical parts as well are severely strained by the repeated starting that is often required, so that the battery can loose its charge quickly, unless the engine starts immediately. Furthermore, these systems require special lines and injection valves for injecting the alcohol fuel, which makes them especially expensive.